Usually, an electronic component is surface-mounted or plug-in mounted on a printed circuit board (hereinafter referred to as PCB), e.g., welded to the PCB through a through-hole in the PCB. In this case, heat generated during the operation of the electronic component is transferred to the outside through the air around the electronic component and through the PCB, to achieve heat dissipation for the electronic component. Since heat-conducting capability of PCB and air is poor, this structure is disadvantageous for the electronic component to dissipate heat, and has especially worse heat dissipation effect for high power electronic component. Hence, it is needed to improve the heat dissipation capability of the electronic component through optimization of assembly design for the plug-in mounting component.
One solution is to mount the electronic component with high demand for heat dissipation onto a metal flange, and connect pins of the electronic component to other circuits through wires. Referring to FIG. 1, a diagram of a conventional structure with the electronic component mounted on a PCB is shown. A groove with two open ends is provided on PCB1, a plurality of electronic components 21 are disposed on a metal flange 22 to be accommodated, as a whole, in the groove on PCB1. The plurality of electronic components 21 are connected to each other through wires, with an input terminal and an output terminal being connected to two pads 11 of the PCB respectively, through which the electronic components 21 are connected to an external input/output circuit. In an application, in a case that the electronic components include an active semiconductor component, an electrode corresponding to one of the pads is a gate of the active component, the electrode corresponding to the other of the pads is a drain of the active component, and the metal flange 22 connected to the bottom of the active semiconductor component serves as a source. A piece of metal 3 for heat dissipation is mounted below PCB1, and the piece of metal 3 for heat dissipation contacts with the metal flange 22, so that the heat generated by the electronic components 21 is conducted through the metal flange 22 to the metal 3 for heat dissipation. A protection cover 5 is provided over the periphery of the electronic components 21. In the electronic component mounting structure, the electronic components 21 and the metal flange 22 are manufactured together as a separate component. In the manufacture process, the PCB manufacturer first makes grooves on the PCB and attaches the piece of metal for heat dissipation on the back of the PCB as required. Then, the electronic components (including the metal flange) provided by the electronic component manufacturer are mounted into the groove through reflow process. Finally, a wiring processing is performed, and a package processing is performed over the area of the electronic components. However, there are such problems in the above manufacturing process:
First, the electronic components and the metal flange are formed as a whole, thus the mounting of the electronic components onto the PCB can only be accomplished by means of the weld paste 4 through the reflow process, and the groove on the PCB has to be of the size greater than that of the metal flange. In this way, there are left and right deviations for the position of the metal flange in the groove, and the deviations in the position cause a defect of uneven length of wires between the electronic components on the metal flange and the PCB. The defect results in a severe impedance fluctuation in some high power devices such as high power RF devices, and reduces consistency of the products.
Second, when manufacturing the product, the PCB manufacturer provides the manufactured PCB to the electronic component manufacturer, the electronic component manufacturer mounts the manufactured electronic components into the PCB and then returns the PCB to the PCB manufacturer for the final reflow and wiring processes. The procedure is tedious and inconvenient, which affects the manufacturing period and product cost adversely.
Thus it is necessary to improve the conventional electronic component mounting structure and manufacturing method, in order to solve the technical problem in conventional processes.